1. Field of the Invention
The present invention relates generally to testing devices and methods of use for same. More specifically, it relates to a testing device and method for shoes. Even more specifically, it relates to a testing device and method for determining the resistance to axial twisting motion in a shoe, and more particularly, to an apparatus and method that allows an indexing of the resistance of various shoes to such a twisting force commonly caused in a shoe during the user's use of the shoe. Even more particularly, it relates to a device and method of testing a shoe that allows the user to determine the proper shoe to purchase due to the unique stresses put on the shoe during the contact, midstance, and propulsion subphases of the user's stance in the case of abnormal pronation. The apparatus and method are especially adapted to effect the correct choice of shoe for individual walking and running characteristics.
2. Description of the Prior Art
Apparatus for axial stress testing of materials in the form of clamping, bending, and measuring apparatus are well known in the art of materials testing. The present invention, however, is unique in that its novel construction allows for quick and easy measuring of a shoe's resistance to axial twisting force.
Athletic shoes, in the last twenty five years, have progressed from canvas high-top "chucks" to today's computer designed, ergonomically proven footwear costing over a hundred dollars a pair. In this interval, the number of people using these athletic shoes, even for everyday wear, has skyrocketed. In this environment, many people make incorrect choices as to the type of shoe that they purchase. With differing body weights and stances during walking or running, some shoes are inappropriate for certain people in that they may flex too easily, thus leading to heel and muscle pain in the foot and lower extremety. The present invention allows for the testing of various shoes to determine the a quantative result that can be used to index the shoe in terms of its resistance to axial torque. In the present invention, the heel of the shoe to be tested is clamped in a fixed position, the portion of the shoe that would be proximate the metatarsal heads of the foot is clamped and torsionally rotated. A calibrated meter is provided to measure the amount of resistance in the shoe.
During a search at the U.S. Patent and Trademark Office, a number of prior art patents were discovered and they are discussed hereinbelow:
U.S. Pat. No. 2,013,643 issued to Elmer J. Bliss on Sep. 10, 1935 discloses a apparatus for the mechanical flexing of shoes. The device has no teaching of any axial twisting force, and the heel of the shoe in this invention is not secured.
In U.S. Pat. No. 2,638,776 issued to Andrew A. Aines on May 19, 1953 there is disclosed a mechanical footwear testing machine. In contrast to the present invention, the heel is not clamped to a fixed point, nor is the device seen to provide any axial torque to the footwear.
Another patent of interest is U.S. Pat. No. 2,799,162 issued to Harold C. R. Carlson on Jul. 16, 1957. This is an apparatus for testing torsion springs. Axial motion is applied to the torsion springs in this case, however, the right or left hand wound spring is placed snugly over an arbor and rests lightly against a pair of pins. A pointer is set, a crankshaft is turned, and then weights are rested on trays to bring the pointer back to zero. This is clearly dissimilar from the present invention, in that no clamping of a shoe heel on one end and lateral clamping of the ball portion of the shoe on the other, as is required by the present invention, is taught in Carlson.
In U.S. Pat. No. 3,608,372 issued to Emerson B. Hovey on Sep. 28, 1971 there is revealed a tester for shoes. The striker applies stress to the forward edge portion of the outsole. Unlike the present invention, there is no clamping of the heel portion and no measurement of the axial flex of the shoe under stress.
U.S. Pat. No. 3,620,071 issued to Louis E. Kelley et al. on Nov. 16, 1971 discloses a method and apparatus for testing materials for resilience and stress. In this device, a strip of material is stretched between two clamps and then twisted. When the twisting shaft is released, the oscillation period of the material is measured. Unlike the present invention, the clamping mechanisms of the Kelley et al. device attach at completely opposite ends of the test material and would not serve to test a shoe, which requires, for the purposes of biomechanical examination, that the heel of the shoe be fixed to a surface.
Next is U.S. Pat. No. 3,919,886 issued to Philip W. Chambley on Nov. 18, 1975. This relates to measuring yarn twist sets. Unlike the present invention, there is no teaching of the clamps required to test the axial rotation of a shoe.
In U.S. Pat. No. 4,096,733 issued to Arnold Cohen on Jun. 27, 1978 there is disclosed a device for testing footwear soles. This is clearly dissimilar from the instant invention in that there are no lateral clamps to hold the edges of the shoe proximate the ball of the foot, as are required in the present invention.
U.S. Pat. No. 4,130,007 issued to Hideki Hayashi on Dec. 19, 1978 teaches a footwear tester in which a footwear block fits inside the shoe to be tested and a prime mover simulates the motion of walking. There are no exterior clamps, no fixed heel portion, and no measurement of the axial resistance of the shoe to torque. Thus, the Hayashi patent is unlike the present invention.
U.S. Pat. No. 4,327,572 issued to F. Judson Pitman et al. on May 4, 1982 discloses a wear tester for shoes. This device drives the sole of a test shoe against an abrasive wear surface in a simulated motion of running. Thus it is clearly dissimilar from the present invention in that no resistance to axial torque is measured.
Another patent of interest is U.S. Pat. No. 4,432,223 issued to Elmer G. Paquette et al. on Feb. 21, 1984. This is a footwear testing apparatus and method and is unlike the present invention in that it is not concerned with measuring the axial resistance of the shoe's sole to torque.
In U.S. Pat. No. 4,958,522 issued to Peter R. McKinlay on Sep. 25, 1990 there is disclosed a shear stiffness tester. No laterally placed clamps are taught by this invention, nor is the instant invention's clamp that holds the heel downwardly against a fixed plate.
U.S. Pat. No. 5,079,955 issued to Allen C. Eberhardt on Jan. 14, 1992 is a method and apparatus for fatigue crack detection and propagation analysis. As in many of the above patents, the clamps required to biomechanically test the shoe are not shown and, additionally, the stress is applied perpendicular to the longitudinal axis of the test specimen.
Lastly, U.S. Pat. No. 5,567,884 issued to Gerard T. Dickinson et al. on Oct. 22, 1996 discloses a circuit board assembly torsion tester and method. Unlike the present invention, the lateral exterior clamps proximate the metatarsal area of the foot, required by the present invention for anatomical reasons, due to the midstance subphase of a user's stance; that is while the weight of the entire body is passing over the foot-these clamps are not taught. Neither is the clamp that holds the heel of the shoe to be tested firmly against a fixed platform.
Thus, while the foregoing body of prior art indicates it to be well known to use various clamps to test various materials under stress, the provision of a more simple and cost effective device as si described below is not contemplated. Nor does the prior art described above teach or suggest the novel clamps of the present invention to measure the resistance in a shoe to the longitudinal axial torsion stress created by walking or running in the sole of a shoe. The foregoing disadvantages are overcome by the unique downwardly fixed interior heel clamp and laterally disposed exterior metatarsal clamps of the present invention as will be made apparent from the following description thereof. Other advantages of the present invention over the prior art will also be rendered evident.